Conventionally, a module for storing and conveying fragile and heavy rectangular thin panels such as solar panels that are stacked in the vertical direction so as not to contact one another has been used. Patent Document 1 discloses an example of this module.
This module includes a support surface and a molded member. The support surface supports a rectangular thin panel from the lower side. The molded member is coupled with the support surface, extends outward from the support surface, and transmits the weight of the rectangular thin panel in the vertical direction. The molded member includes a recess or a protrusion on each of the upper and the lower portions. The recess and the protrusion can fit each other. This module is placed at each of the four corners of the rectangular thin panel, which is supported by a rectangular-shaped annular outer frame at the peripheral edge. The rectangular thin panel is placed on each support surface of this module via the outer frame. Then, in each corner, the recess at the lower portion of the molded member in a new module is fitted to the protrusion at the upper portion of the molded member in a module that is already disposed. Similarly, the next rectangular thin panel is supported by four modules. Accordingly, the rectangular thin panels can be stacked in the vertical direction so as not to contact one another.
However, as for this module, in the case where the rectangular thin panel is conveyed with a pallet in a state where each of the four corners of the rectangular thin panel without the outer frame is placed on the support surface of this module, the following technical problem arises. The rectangular thin panel is at risk of damage or breakage during conveyance. More specifically, for example, in the case where stacked rectangular thin panels are transported by a motortruck, or in the case where a pallet runs over an uneven road surface, the rectangular thin panel vibrates and the maximum amplitude in the vertical direction occurs almost in the center of the rectangular thin panel. At this time, each corner portion of the rectangular thin panel, which is placed on the support surface of the module, is a free end. The amplitude in the center of the rectangular thin panel tends to be amplified more than the case where an outer frame makes each corner portion a fixed end. This vibration or collision with support portions above and below may cause damage of the rectangular thin panel and may lead to breakage of the rectangular thin panel in some cases. On the other hand, there are various forms of rectangular thin panels. Some rectangular thin panels are required to be conveyed in a state where they are stacked nakedly without any outer frame.    Patent Document 1: JP-A-2006-32978